1. During the steady state measurement, [S] certainly decreases (after all, product is being formed). Consequently [ES] must also decrease. However, the assumption is that it does not decrease during the measurement. Therefore b) is the best answer.
2. This is an important feature of the Michaelis Menten equation, i.e. when [S] = KM, the denominator = 2 and vo = VMAX/2.
3. KM is never less than Kd because as shown in Eqn. 6.11 in Campbell, KM has the additional k2 term in the numerator. In other words, KM is always greater than or equal to Kd.
4. KM provides information of substrate binding since it is related to (but not equal to) KD. VMAX or kCAT provide information related to the chemical step of the reaction; VMAX= ET kCAT.
5. The initial velocity approaches Vmax at high [S], but only reaches Vmax as an extrapolation to infinite [S], i.e. 1/[S] -->0.
6. After taking the reciprocal of the rate equation you get: (1/v) = KM/VMAX (1/[S]) + 1/VMAX. Therefore c) is correct.
7. This fractional activity relationship is identical to the fraction saturation concepts of ligand binding.
8. This fractional activity relationship is identical to the fraction saturation concepts of ligand binding.
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